What are cumulonimbus clouds? Cumulonimbus clouds are menacing looking multi-level clouds, extending high into the sky in towers or plumes. More commonly known as thunderclouds, cumulonimbus is the only cloud type that can produce hail, thunder and lightning.

What are considered high clouds?

High-level clouds occur above about 20,000 feet and are given the prefix “cirro.” Due to cold tropospheric temperatures at these levels, the clouds primarily are composed of ice crystals, and often appear thin, streaky, and white (although a low sun angle, e.g., near sunset, can create an array of color on the clouds).

How high do cumulonimbus clouds reach?

Fueled by vigorous convective updrafts (sometimes in excess 50 knots), the tops of cumulonimbus clouds can easily reach 39,000 feet (12,000 meters) or higher.